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4.10 or 4.56

79bonanza

79bonanza

1/2 ton status
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Georgetown, Kentucky
Hey let me start off by saying I have looked into this but I still can't make up my mind.

My K5 has a 5.3L 4L60E and an np241. It's on 33x12.50 right now.

I plan on running a 35x12.50 in the near future, this is where it gets tricky. It's gonna be a DD/expedition style build. So I want the truck to get decent mileage for long highway trips. Like 70-80 mph and cruise set. But I also want it to be able to go down the trails and have low enough gears for some mild crawling.

I've looked up the rpm gear ration calculator and it said with a 4.10 gear at 70 mph I'd be in the 1900 rpm range, with a 4.56 it's around 2100.

I can't decide. 4.10 or 4.56. What's your guys thought
 
For a DD on 35's I'd say 4.10

With 4.56's you might be keeping it wound a little tight on the Interstates and such.

Before you jump the gun, put a tape measure and level out to you tire and see how tall they really are. Don't go by the number on the tire. (They are made by men for men, and what do we do with numbers involving size? Be it a fish, a deer, or our tires. A:+2 :haha:) then go back and run your numbers again. Then go dive a stock vehicle with a tach and figure out what works for where and how you drive.
 
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going with 35's, I'd do 4.56. I have 4.10's with 35's and it lugs at times and sometimes hunts back and forth from 3rd to 4th.
 
4.56

No exp with the 4L60, but I know with my 700r4 (and AFAIK they're nearly the same), the absolute last thing you want is for the trans to be searching for 4th like 4xcrazy said. Hunting 3-4 and lock/unlocking over and over again will EAT a transmission.

It's a fine line playing with gears, it's not just a one component decision, it's everything working in a balance. 2100 is not a high RPM by any means, and more importantly, that's closer to the stock figures than the 1900 with the 4.10s. Cruising down the highway at 2100rpm isn't what's going to eat your gas, nor is it screaming your engine.



IMO, people don't go deep enough. Here's stock figures to make some comparisons.

Final Drive: 3.73
Tire Height: 30 (stock was 235 IIRC, with 31" optional, so I averaged)
MPH:70
Transmission Final Gear: .70 (OD)
RPM: 2047

Same as above with 4.56 and 35s is 2145, 4.10s is 1945. If you look at a lot of Tire/Gear charts, 4.56/4.88 puts you back in the middle of your economy/power curve, where 4.10 is in the economy side.

And as far as crawling, you're fine with either. I was barely touching my throttle with 3.08s and 33s :waytogo:
 
I have a stock 350, 91k5 with true 35s and 4:88 gears, I love it! The mpg between 4:56 and 4:88 is not enough to worry about. 4:10 gears it would be down shifting at every over pass or little hill
 
72blazerguy said:
4.56 will be great. 2100 rpm is a great cruising rmp for that motor.
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Agreed. That 2-300 rpm difference is nothing once you figure in all the camping/expo type gear packed into the truck, you'll be better off with the 4.56s.

Now, I run mine with 4.10s and 35s, and I'm not wanting for more gear. BUT, I run my truck with as little weight as possible (topless most of the year and zero interior, just seats) AND I live at sea level. Long road trips and potentially into/over/through the mountains or whatnot, I'd go 4.56s at least.
 
Don't do 4.10. My stock 350/700/33" setup is perfect with 4.10's. So, if you're talking about a bigger tire, and a motor that likes higher revs, you'll want to go 4.56.
 
nothing more annoying than a hunting OD trans... well, except maybe a PMS-ing fat chick....
 
:haha: :bow:


I know fat chicks need lovin too, but somehow, it just made sense... :pimp:
 
I went blank in the gear ratios when I posted about the 4.56's, but with my Suburban with the rebuilt TBI 350, rebuilt TH700r4, 35" tires and 4.10's currently, it does drive fine, BUT,,,,BUT,,, I really need to be listening to the engine while driving, paying attention to what it's doing if I'm in hills or whatnot. It does hunt between lock-up and non, which still creates heat.

I just recently burnt up a 4L60e in the '05 Avalanche because I let it hunt in and out of lock up of the torque converter. Yeah, something THAT simple killed the trans on a return trip from California to Phoenix.

Overheated it, and it didn't shift right ever since. $1200 and a few days of my labor out the door because I failed to simply press a button on it that said "tow/haul mode" or just drop it to 3rd gear and let the engine rev and deal with the lower MPG's.

So, I listen now, usually don't even have the stereo up very loud much anymore and even if I do, I'm constantly watching the rpm's and still trying to listen to what all the drivetrain is doing.

This went too long in to posting, but what I intentionally wanted to say, was with the weight of the Burb, and potential for towing that I tend to do often, I do plan, myself, on going with at least 4.88's.


So it really depends on your use. If you plan on doing any towing, regularly, maybe consider that gear ratio.. it'sll also be that lower gear that will help on the trails too. :tongue1:
 
I agree with 4.56's. In this situation you want to gear the axles to optimal highway performance. While crawling off-road there is no basically no difference between 4.10 and 4.56...never been on a trail ride and heard somebody say "man, if I just had 4.56 gears instead of 4.10 I could have made that obstacle". The 4L60 and 241 combination provide a pretty good crawl ratio and is the best combination (in regards to gearing) ever offered in a K5. For example a 4L60/700r4 and 241 combo with 4.10 gears gives a 34:1 crawl ratio. A TH400 and 205 combo with the same axles is only 20:1.
 
6.2Blazer said:
The 4L60 and 241 combination provide a pretty good crawl ratio and is the best combination (in regards to gearing) ever offered in a K5 (with an automatic). For example a 4L60/700r4 and 241 combo with 4.10 gears gives a 34:1 crawl ratio. A TH400 and 205 combo with the same axles is only 20:1.
Click to expand...

Fixed it for you.
 
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